Nucleic acid hybridization assays comprise an important class of techniques in modern biology. Such assays have diverse applications including the diagnosis of inherited disease, human identification, identification of microorganisms, paternity testing, virology, and DNA sequencing, i.e., sequencing by hybridization.
An important aspect of nucleic acid hybridization assays is the method used to facilitate detection of the hybridization event. A particularly important class of methods used in nucleic acid hybridization assays employs a reporter-quencher energy-transfer dye pair comprising a “reporter” dye and a “quencher” dye which interact through a fluorescence resonance energy transfer (FRET) process. In these methods, the reporter is a luminescent compound that can be excited either by chemical reaction, producing chemiluminescence, or by light absorption, producing fluorescence. The quencher can interact with the reporter to alter its light emission, usually resulting in the decreased emission efficiency of the reporter. This phenomenon is called quenching. The efficiency of quenching is a strong function of the distance between the reporter molecule and the quencher molecule. Thus, in a nucleic acid hybridization assay, detection of a hybridization event is accomplished by designing an energy transfer system in which the spacing between a reporter and a quencher is modulated as a result of the hybridization.
Quenchers which are presently used in FRET-based nucleic acid hybridization assays are themselves fluorescent. That is, in addition to quenching the fluorescence of the reporter, the quencher produces fluorescent emissions. This is problematic, particularly in assays employing multiple spectrally-resolvable reporters, because the quencher fluorescence can interfere with the fluorescent signal produced by one or more of the reporters.
Thus, there remains a continuing need for quencher dyes which are themselves substantially non-fluorescent.